I got a long bone from a hill giant. what do i do with it if i want to sell it for money because its non tradable. The prayer guide says it can be sold somewhere for money but where?

take it to the dogershunn goblins. they're under lumby castle. You have to do lost tribe quest.

Better wait until you have a couple more, so that it's worth the trouble getting down there and finding Barlak, the npc that buys them. He's at ground (sort of) floor, east side. North-east corner then south (no stair climbing)

He'll give you some money (around 2k if I remember correctly) and similar construction exp for each long or curved bone.